It stands to reason that if you're going to be running wires over the entire field you wouldn't need flying drones so much as you would need cameras on wheels (

It stands to reason that if you're going to be running wires over the entire field you wouldn't need flying drones so much as you would need cameras on wheels (like they have at football stadiums). If the camera sees the correct spectra for a known weed it can drop down and get a closer inspection then mark the spot or just burn the weeds with an attached laser. I assume the crawler is necessary because--in order for the laser to work--the weeds need to be identified very early as they emerge from the ground. You might not be able to spot them at such an early stage from above without expensive optics.